The present invention is generally directed to an amplitude control for controlling the peak amplitude of an oscillator output alternating voltage and more particularly to an improved regulating system of the type which converts a DC voltage to an alternating voltage of controlled peak amplitude.
Regulating systems for converting a DC voltage to an alternating output voltage of constant peak amplitude are well-known in the art. Such systems generally include an oscillator which converts the DC voltage to an alternating voltage. Regulation is obtained by utilizing a series pass transistor coupled between the DC voltage source and the collector of the oscillator transistor to control the amount of current available to the oscillator. In doing so, the peak amplitude of the alternating output voltage may be controlled.
Regulating systems of this type find considerable application in devices such as image intensifiers where a high constant voltage at low current is required. In such devices, a voltage multiplier multiplies and rectifies the oscillator regulated alternating output voltage, which may be of the order 500 volts peak-to-peak amplitude, to a DC voltage in the order of 8,000 DC. Because image intensifiers and other similar devices must be of small size, the DC voltage to be converted is usually supplied by a small battery delivering a DC voltage of as low as 2 volts.
Prior art systems of this type have been generally satisfactory because of their small size and regulating ability. However, prior art systems experience difficulty when operation at low temperatures and at low values of DC battery supply voltage is required. At low temperatures amplitude stability of prior art systems begins to fail because the forward voltage drop of the series pass transistor adds to the oscillator characteristic which also tends to increase in forward drop due to the decreased conduction of the oscillator transistor. Also, because the oscillator draws current in pulses over only small portions of its cycle, the pass transistor is required to supply relatively high peak currents with a small forward voltage drop.
It is therefore a general object of the present invention to provide a new and improved amplitude control for an oscillator circuit which controls the peak amplitude of the oscillator alternating output voltage.
It is another object of the present invention to provide a new and improved regulating system of the type which converts a DC voltage to an alternating voltage of regulated peak amplitude.
It is a still more particular object of the present invention to provide a new and improved regulating system for converting a DC voltage to an alternating voltage of constant peak amplitude having regulating characteristics which are substantially more stable over wide temperature ranges than heretofore obtainable with systems of the prior art.